In double flywheels, there is a need for large angular displacements between the two rotating masses. For a given capacity to transmit torque, the greater the displacement, the more must the resilient means be elongated, to such an extent that an impossible situation is soon reached.
In addition, for a given arrangement of the resilient means, it is important not to add to the radial bulk of the arrangement to the detriment of the mass of the flywheel lying radially outside the resilient means, since this would increase the value of the resonant frequency.